Connector assembly for active implantable medical device

ABSTRACT

An implantable medical device includes a cover assembly and a feedthrough assembly that couples with the cover assembly. The cover assembly receives a connector end of a lead having lead contacts, and aligns the lead contacts with pockets or apertures of the cover assembly. The feedthrough assembly may include feedthrough contacts in the form of feedthrough pins at or above a surface of a feedthrough substrate, or conductive vias on the surface of the substrate. Electrical contacts configured as leaf spring contact assemblies, torsion spring contacts, or torsion spring contact assemblies are permanently attached to the feedthrough contacts. When the cover assembly and feedthrough assembly are coupled, contact tabs of the electrical contacts are positioned in the pockets or apertures of the cover assembly. Upon complete seating of the cover assembly and feedthrough assembly, the contact tabs are compressed into contact with the lead contacts.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.17/213,138, filed on Mar. 25, 2021, entitled “Connector Assembly ForActive Implantable Medical Device,” which is expressly incorporated byreference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to active implantable medicaldevices, and more particularly, to a connector assembly for activeimplantable medical devices that provides electrical connection betweenelectronics within a housing of the device and electrical leads coupledto the device.

BACKGROUND

Known connector assemblies for implantable medical devices utilizestamped compressive leaf contacts, e.g., see U.S. Pat. No. 6,662,035.These connector assemblies include a clamping cover with one or moreelastomeric seals configured to receive leads, and a feedthroughassembly that includes compressive leaf contacts, and to which theclamping cover connects. The compressive leaf contacts are attached tofeedthrough pins of the feedthrough assembly by laser welding. A lead isreceived in a separate elastomeric seal of the clamping assembly. Thelead contacts engage the compressive leaf contacts via apertures in theseal when the clamping cover is fully seated with the feedthroughassembly, or in other words, when the connector assembly is pressurized.

SUMMARY

A connector assembly of an implantable medical device includes a coverassembly and a feedthrough assembly configured to couple with the coverassembly. The cover assembly is configured to receive a connector end ofa lead having lead contacts, and to align the lead contacts with pocketsor apertures of the cover assembly. The feedthrough assembly may includefeedthrough contacts in the form of feedthrough pins at or above asurface of a feedthrough substrate, or conductive vias on the surface ofthe substrate. Electrical contacts configured as leaf spring contactassemblies, torsion spring contacts, or torsion spring contactassemblies are permanently attached to the feedthrough contacts throughan attachment feature of the contacts. When the cover assembly andfeedthrough assembly are coupled, contact engagement features of theelectrical contacts are positioned in the pockets or apertures of thecover assembly. Upon complete seating of the cover assembly andfeedthrough assembly, the contact engagement features are compressedinto contact with the lead contacts.

A connector assembly of an implantable medical device includes a coverassembly and a feedthrough assembly configured to couple with the coverassembly. The cover assembly is configured to receive a connector end ofa lead having lead contacts, and to align the lead contacts with pocketsor apertures of the cover assembly. The feedthrough assembly may includefeedthrough contacts in the form of feedthrough pins at or above asurface of a feedthrough substrate, or conductive vias on the surface ofthe substrate. Electrical contacts configured as contact ring assembliesor leaf spring contacts are retained by, but not permanently attachedto, one of the feedthrough assembly or the cover assembly. When thecover assembly and feedthrough assembly are coupled, first surfaces ofthe electrical contacts face the feedthrough contacts and secondsurfaces of the contacts are positioned in the pockets or apertures ofthe cover assembly. Upon complete seating of the cover assembly andfeedthrough assembly, the first surfaces and second surfaces of theelectrical contacts are respectively compressed into contact with thefeedthrough contacts and the lead contacts.

It is understood that other aspects of apparatuses and methods willbecome readily apparent to those skilled in the art from the followingdetailed description, wherein various aspects of apparatuses and methodsare shown and described by way of illustration. As will be realized,these aspects may be implemented in other and different forms and itsseveral details are capable of modification in various other respects.Accordingly, the drawings and detailed description are to be regarded asillustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of apparatuses will now be presented in the detaileddescription by way of example, and not by way of limitation, withreference to the accompanying drawings, wherein:

FIG. 1 is an illustration of a connector assembly that includes a coverassembly and a feedthrough assembly, wherein the cover assembly isdecoupled from the feedthrough assembly and the feedthrough assemblyincludes separable or detached, i.e., interposed, contacts configured ascontact ring assemblies.

FIG. 2A is a cross-section view of the cover assembly of FIG. 1 alongline A-A and showing the cover assembly from underneath.

FIG. 2B is an exploded illustration of the cover assembly of FIG. 1 .

FIG. 3 is an exploded illustration of the feedthrough assembly of FIG. 1including a pair of electrical contact interposer assemblies and afeedthrough subassembly.

FIG. 4 is an exploded illustration of an electrical contact interposerassembly of FIG. 3 including contact ring assemblies, a contactretainer, and a lower seal.

FIG. 5 is an exploded illustration of a contact ring assembly of FIG. 4.

FIG. 6 is an enlarged version of the illustration of FIG. 3 .

FIG. 7 is a cross-section view of a portion of the connector assembly ofFIG. 1 along line B-B.

FIG. 8 is cross-section view of a portion of an electrical contactinterposer assembly showing a contact ring assembly retained by acontact retainer.

FIGS. 9A and 9B are plan views of an electrical contact interposerassembly.

FIG. 10A is a cross-section view showing an initial engagement of acover assembly to a feedthrough assembly.

FIG. 10B is a cross-section view showing a full assembly of a coverassembly to a feedthrough assembly.

FIG. 11 is a graph corresponding to the theoretical stress-strain curveof super-elastic nitinol.

FIG. 12 is a graphical representation of the levels of stress of acontact ring assembly under radial compression.

FIG. 13 is a graph representing force-displacement behavior of differentgeometries during radial compression.

FIGS. 14A and 14B are illustrations of a contact ring assembly includinga contact ring and a backing ring.

FIGS. 14C-17B are illustrations of different embodiments of backingrings.

FIGS. 18A-19B are illustrations of different embodiments of electricalcontact interposer assemblies.

FIG. 20 is a cross-section view of a feedthrough assembly having aleadless feedthrough subassembly.

FIG. 21 is a cross-section view of a portion of a connector assemblythat includes a cover assembly and a feedthrough assembly, wherein thefeedthrough assembly includes contacts configured as leaf spring contactassemblies that are inseparable from, or permanently attached to thefeedthrough assembly.

FIG. 22 is a cross-sectional view, taken across the leaf spring contactassemblies of the connector assembly of FIG. 21 .

FIG. 23 is an illustration of the feedthrough assembly of FIG. 21 .

FIG. 24 is a cross-sectional view of the feedthrough assembly of FIG. 23along line A-A.

FIG. 25 is a disassembled view of the leaf spring contact assembly ofFIG. 23 including a compressive contact and an elastic mount.

FIG. 26 is a perspective view of a leaf spring contact assembly of FIG.23 .

FIG. 27 is a side view of the leaf spring contact assembly of FIG. 26 ,showing the compressive contact joined to the elastic mount by welding.

FIG. 28 is an illustration of another feedthrough assembly with contactsconfigured as leaf spring contact assemblies that may be used in placeof the feedthrough assembly of FIG. 23 .

FIG. 29 is a cross-sectional view of the feedthrough assembly of FIG. 28along line A-A.

FIGS. 30 and 31 are different perspective illustrations of the leafspring contact assembly of FIG. 28 including a compressive contact and aU-shaped mount.

FIG. 32 is a disassembled view of a leaf spring contact assembly of FIG.31 .

FIG. 33 is an illustration of the feedthrough assembly of FIG. 28 withthe compressive contacts of the leaf spring contact assemblies removedfrom the U-shaped contact mounts.

FIG. 34 is a top view of a portion of the feedthrough assembly of FIG.28 .

FIG. 35 is an illustration of a feedthrough assembly with another formof leaf spring contact assemblies.

FIG. 36 is a perspective illustration of a leaf spring contact assemblyof FIG. 35 including a compressive contact and a U-shaped mount.

FIG. 37 is a visualization of the forming of the compressible contact ofthe leaf spring contact assembly of FIG. 36 .

FIG. 38 is an illustration of the compressible contact of the leafspring contact assembly of FIG. 36 .

FIG. 39 is an illustration of a connector assembly that includes a coverassembly and a feedthrough assembly, wherein the cover assembly isdecoupled from the feedthrough assembly and the feedthrough assemblyincludes contacts configured as torsion spring contacts that areinseparable from, or permanently attached to the feedthrough assembly.

FIG. 40 is an illustration of the cover assembly of FIG. 39 with thefeedthrough side of the cover assembly facing up, to reveal seals.

FIG. 41 is a cross-sectional view of the connector assembly of FIG. 39when the cover assembly is coupled to, but not fully seated with thefeedthrough assembly, taken along the lead.

FIG. 42 is a cross-sectional view of the connector assembly of FIG. 39when the cover assembly is coupled to, but not fully seated with, thefeedthrough assembly, taken at a right angle to the leads.

FIG. 43 is an enlarged detail view of a portion of the feedthroughassembly of FIG. 39 showing a torsion spring contact raised above adielectric substrate of the feedthrough assembly.

FIG. 44 is an enlarged top view of a portion of the feedthrough assemblyof FIG. 39 showing a torsion spring contact occupying a counterbore ofthe dielectric substrate.

FIG. 45 is a partial cross-sectional view of the feedthrough assembly ofFIG. 41 showing a torsion spring contact in free state, confined in acounterbore of a dielectric substrate.

FIG. 46 is a partial top view of the feedthrough assembly of FIG. 41 ,showing a torsion spring contact within counterbore of a dielectricsubstrate.

FIG. 47 is a partial cross-sectional view of the feedthrough assembly ofFIG. 41 showing a torsion spring contact with increased clearancebetween a free side of the contact and an inside wall of a counterboreof a dielectric substrate.

FIG. 48 is a partial top view of the feedthrough assembly of FIG. 41 ,showing a torsion spring contact with increased clearance between a freeside of the contact and an inside wall of a counterbore of a dielectricsubstrate.

FIG. 49 is an isometric view of the torsion spring contact of FIG. 41 ina free state.

FIG. 50 is an upside-down view of the torsion spring contact of FIG. 49.

FIG. 51 is an isometric view of the torsion spring contact of FIG. 49with contact force applied, showing contact deflection and resulting VonMises stress.

FIG. 52 is a side view of the torsion spring contact of FIG. 49 withcontact force applied, showing contact deflection and resulting VonMises stress.

FIG. 53 is an illustration of a contiguous piece of material in a flatpattern and from which the torsion spring contact of FIG. 45 is formed.

FIG. 54-58 provide visualization of the torsion spring contact formingsteps, showing that the two sides of the contact can be formedsimultaneously without interference.

FIG. 59 is an exploded view of another contact configured as a torsionspring contact assembly that includes a torsion spring contact and aweld plate.

FIG. 60 is an upside-down perspective view of the torsion spring contactassembly of FIG. 59 .

FIG. 61 is a partial perspective view of a feedthrough assembly with thetorsion spring contact assembly of FIG. 59 raised above a dielectricsubstrate of the feedthrough assembly.

FIG. 62 is a partial top view of a feedthrough assembly showing thetorsion spring contact assembly of FIG. 59 occupying a counterbore ofthe dielectric substrate.

FIG. 63-64 is an illustration of another contact configured as a torsionspring contact assembly that includes a torsion spring contact and aprotective shroud.

FIG. 65 is a partial perspective view of a feedthrough assembly with thetorsion spring contact assembly of FIG. 63 raised above a dielectricsubstrate of the feedthrough assembly.

FIG. 66 is a cross-sectional view of a connector assembly taken along alead when a cover assembly is coupled to, but not fully seated with afeedthrough assembly having contacts configured as torsion springcontacts attached to feedthrough pins.

FIG. 67 is a cross-sectional view of the connector assembly of FIG. 66taken at a right angle to a pair of leads when a cover assembly iscoupled to, but not fully seated with a feedthrough assembly.

FIG. 68 is a partial perspective view of a feedthrough assembly showinga torsion spring contact of FIGS. 66 and 67 at least partially raisedabove a counterbore of a dielectric substrate of the feedthroughassembly.

FIG. 69 is enlarged view of the torsion spring contact of FIG. 68 .

FIG. 70 is a partial top view of the feedthrough assembly of FIG. 68 ,showing torsion spring contacts coupled to feedthrough pins, and withincreased clearance between a free side of the contacts and an insidewall of the counterbore.

FIG. 71 is a partial cross-sectional view of the feedthrough assembly ofFIG. 68 showing torsion spring contacts coupled to feedthrough pins, andwith increased clearance between a free side of the contacts and aninside wall of the counterbore.

FIGS. 72-75 are illustrations of another contact configured as a torsionspring contact configured to occupy a counterbore in a dielectricsubstrate and to attach to a feedthrough pin at the bottom of thecounterbore.

FIGS. 76-79 are illustrations of another contact configured as a torsionspring contact configured to occupy a counterbore in a dielectricsubstrate and to attach to a feedthrough pin that extends upward fromthe bottom of the counterbore.

FIGS. 80-83 are illustrations of another contact configured as a torsionspring contact configured to occupy a counterbore in a dielectricsubstrate and to attach to a feedthrough pin that extends above thecounterbore.

FIGS. 84 and 85 are illustrations of a connector assembly that includesa cover assembly and a feedthrough assembly, wherein the cover assemblyis decoupled from the feedthrough assembly and the feedthrough assemblyincludes contacts configured as leaf spring contacts that are retainedby the cover assembly.

FIGS. 86A and 86B are an enlarged views of the leaf spring contact ofFIG. 85 from different perspectives.

FIG. 87 is a cross-sectional view of the connector assembly of FIG. 84with the cover assembly coupled to the feedthrough assembly, but notfully seated.

FIG. 88 is a detail view of a portion of FIG. 87 .

FIG. 89 is a detailed plan view of a leaf spring contact retained by thecover assembly of FIG. 85 .

FIG. 90 is a cross-sectional view of the connector assembly of FIG. 84with the cover assembly coupled to the feedthrough assembly, and fullyseated.

FIG. 91 is a detail view of a portion of FIG. 90 .

FIG. 92 is a perspective cross-sectional view of a dual-lumen seal ofthe cover assembly of FIGS. 84 and 85 , taken across seal apertures, toreveal contact retention ledges.

FIG. 93 is a detailed cross-sectional view of the seal of FIG. 92revealing a retained leaf spring contact.

FIG. 94 is a perspective cross-sectional view of a dual-lumen seal,taken along seal apertures, to reveal concave contact retentionfeatures.

FIG. 95 is a detailed cross-sectional view of the seal of FIG. 94 , witha leaf spring contact snapped in place from the feedthrough side of theseal, and retained by the seal's concave contact retention features.

FIGS. 96-99 are various embodiments of leaf spring contacts that may beused in the connector assembly of FIGS. 84 and 85 .

FIG. 100 is a plan view illustration of a conventional feedthroughassembly that accommodates two leads.

FIG. 101 is a plan view illustration of a feedthrough assembly disclosedherein that that accommodates four leads in about the same amount ofspace as the conventional feedthrough assembly of FIG. 100 .

DETAILED DESCRIPTION

Disclosed herein are various types of connector assemblies forimplantable medical devices. The connector assemblies disclosed providemeans of establishing electrical interconnection between electronicswithin a housing of an active implantable medical device and electricalleads coupled to the device. The connector assemblies include a coverassembly having ports, each for receiving a connector end of a lead, anda feedthrough assembly having feedthrough contacts. The cover assemblyis configured to couple to the feedthrough assembly and establishelectrical connection between lead contacts at the connector ends of thereceived leads and the feedthrough contacts. The electrical connectionis provided in part by contacts of the connector assembly that arelocated between the lead contacts and the feedthrough contacts. In someconfigurations, the contacts are associated with the feedthroughassembly. In other configurations, the contacts are associated with thecover assembly.

In some embodiments the connector assemblies disclosed hereinaccommodate four leads in about the same amount of space as aconventional connector assembly that accommodates only two leads.Accordingly, the connector assemblies can be designed into a modifiedimplantable medical device without having to expand the size of thedevice. The connector assemblies may include four lines of contacts,where each line of contacts is arranged to couple with a correspondingline of lead contacts at the connector end of a lead. In order to doublethe contact density, the disclosed connector assemblies use smallercompressive contacts with ring configurations, leaf springconfigurations, or torsion spring configurations, which assure adequatecontact deflection capability in a smaller contact footprint. Thecontacts are disposed in-line with the lead to enable using twodual-lumen seals, each seal receiving two leads with lead-to-leadspacing of approximately 2 mm.

The contacts may be associated with the feedthrough assembly and may bedetached, ring contacts or leaf spring contacts retained in a supportstructure. In other configurations disclosed herein, the contacts may beleaf spring contacts or torsion spring contacts that are attached tofeedthrough contacts. In other embodiments the contacts may beassociated with the cover assembly. For example, the contacts may bedetached, leaf spring contacts retained in an elastomeric seal of thecover assembly.

I. Contacts Associated with Feedthrough Assembly

Connector assembly contacts may be associated with the feedthroughassembly in either of two ways. In one configuration, the contacts aresecurely retained in a contact retainer of the feedthrough assemblythrough respective mechanical features of the contacts and the contactretainer in a way that prevents movement of the contacts within thecontact retainer, even when a cover assembly is removed from thefeedthrough assembly. Upon coupling of the cover assembly to thefeedthrough assembly, the contacts are further retained by a contactforce between two conductive elements that compresses the contacts. Thecontacts in this configuration may be generally described herein asbeing separable or detached because the contacts are not welded orbonded within the contact retainer, but instead are retained in a waythat allows for compression or pressure connection between the contacts,the lead contacts, and the feedthrough contacts when a cover assembly iscoupled to the feedthrough assembly. These detached, separable contactsmay be referred to herein as “interposer” contacts. In anotherconfiguration, the contacts are securely retained in a feedthroughassembly through bonding. For example, the contacts may be covalentlybonded to the feedthrough contacts of the feedthrough assembly by alaser welding process. The contacts in this configuration may begenerally described herein as being inseparable or attached.

A. Feedthrough Assembly with Detached Contact Ring Assemblies

With reference to FIGS. 1-19B, a connector assembly 100 of animplantable medical device includes a cover assembly 102 and afeedthrough assembly 104 configured to couple with the cover assembly.The cover assembly 102 is configured to receive a connector end of alead 106 having lead contacts 1002, and to align the lead contacts withpockets or apertures 210 of the cover assembly. The feedthrough assembly104 may include feedthrough contacts 314 in the form of feedthrough pins312 at or above a surface of a feedthrough substrate 310, or conductivevias on the surface of the substrate. Electrical contacts 402 configuredas contact ring assemblies are retained by, but not permanently attachedto, the feedthrough assembly 104. When the cover assembly 102 andfeedthrough assembly 104 are coupled, first surfaces 1004 of theelectrical contacts 402 face the feedthrough contacts 314 and secondsurfaces 1006 of the contacts are positioned in the pockets or apertures210 of the cover assembly. With reference to FIG. 10B, upon completeseating of the cover assembly 102 and the feedthrough assembly 104, thefirst surfaces 1004 and second surfaces 1006 of the electrical contacts402 are respectively compressed into contact with the feedthroughcontacts 314 and the lead contacts 1002.

With reference to FIGS. 2A and 2B, the cover assembly 102 includes acover 202, a pair of upper seals 204, and a screw 206. The upper seals204 may be made of silicone and are sized to fit at least partiallywithin recesses 212 formed in the bottom of the cover 202. The upperseals 204 may be bonded into the recesses 212 with a silicone adhesive.Each upper seal 204 includes two lead ports 208, each configured toreceive a proximal end, or connector end of a lead. The proximal end ofthe lead has a number of lead contacts. Apertures 210 in the upper seals204 allow access between the lead contacts of a lead positioned in alead port 208 and feedthrough contacts of a feedthrough assembly 104.The screw 206 is retained in the cover 202 and is configured to secureto a corresponding hole in the feedthrough assembly.

With reference to FIG. 3 , the feedthrough assembly 104 includes afeedthrough subassembly 302 and an electrical contact interposerassembly 304. The feedthrough subassembly 302 includes a feedthroughferrule 306 with a pair of rectangular recesses 308, each with afeedthrough substrate 310 fitted therein. A number of feedthrough pins312 pass through the feedthrough substrate 310 providing an electricalconduction path between opposite sides of the feedthrough ferrule 306.Each of the feedthrough pins 312 has a head 314 on the recess side ofthe feedthrough ferrule 306. The head 314 may be referred to as afeedthrough contact.

With reference to FIG. 4 , the electrical contact interposer assembly304 includes a number of electrical contacts 402 configured as contactring assemblies, a lower seal 404, and a contact retainer 406. Thecontact ring assemblies 402 and contact retainer 406 are configured sothat the contacts are retained by the contact retainer. To this end, inone configuration, the contact ring assemblies 402 include tabs 506configured to be positioned within retention slots 408 of the contactretainer 406 and to interfere with the contact retainer in a way thatprevents movement of the contacts relative to the contact retainer. Inone configuration, the contact retainer 406 is an injection moldedcomponent made of Polyetheretherketone (PEEK). The contact retainer 406may also be made of other materials such as liquid crystal polymer(LCP). The lower seal 404 is a molded component made of a siliconerubber which fits into a mating recess in the contact retainer 406.

With reference to FIG. 5 , in one configuration the contact ringassemblies 402 are configured as contact ring assemblies, each of whichincludes a contiguous backing ring 502 and a contiguous contact ring504. The backing ring 502 includes a pair of retention tabs 506. Thebacking ring 502 may be made of nitinol, which is a super-elasticmaterial that provides sufficient contact force and elastic range whensqueezed between the feedthrough pin 312 and a lead contact. The forcenecessary to establish an electrical contact may be greater than 50grams. The necessary elastic range of the backing ring 502 is dependentupon the design of the lower seal 404 and the physical space toaccommodate the backing ring.

In one embodiment, the outside diameter of the backing ring 502 isapproximately 1.3 mm. The outside diameter of the backing ring 502 mayrange from 1-2 mm depending on the required range of elastic deflectionand available physical space to accommodate the ring. The wall thicknessof the backing ring 502 may vary from 0.02-0.10 mm. The wall thicknesshas a significant effect on contact force and elastic range of thebacking ring 502. The width of the backing ring 502 may vary from 0.5-2mm depending on the required range of contact force and availablephysical space to accommodate the ring. In one specific configuration,the backing ring 502 a wall thickness of 0.04 mm, an outside diameter of1.3 mm and width of 0.7 mm. The backing ring 502 includes tabs 506 thatfacilitate retaining the rings in contact retainer 406.

In some embodiments, the contact ring 504 is made of a 90-10platinum-iridium alloy. The contact ring 504 is sized to fit over thebacking ring 502 and provides electrical contact between the feedthroughpins 312 and the lead contacts. The contact ring 504 is approximatelyequal in width to the backing ring 502. The inside diameter of the ofthe contact ring 504 is approximately equal to or slightly larger(0.002-0.01 mm) than the outside diameter of the backing ring 502. Aslip fit between the backing ring 502 and the contact ring 504facilitates assembly. An interference fit between the two rings 502, 504may be suitable given alternate embodiments of the contact ring assembly402. The wall thickness of the contact ring 504 is approximately 0.025mm. Due to the ductal property of the contact ring 504, the contact ringdoes not slip axially over the backing ring 502, after the assembly iscompressed radially.

With reference to FIGS. 6 and 7 , undercuts 602 are machined into thefeedthrough ferrule 306. These undercuts 602 mate with tabs 604 on thecontact retainer 406. The mating features serve to retain the electricalcontact interposer assemblies 304 in the feedthrough subassembly 302.The tabs 604 provide a snap-in feature during assembly that retains theelectrical contact interposer assemblies 304 in the feedthroughsubassembly 302. In one embodiment, the centers of the tabs 604 of thecontact retainer 406 are aligned parallel with the center axis of thecontact ring assemblies 402.

With reference to FIGS. 8, 9A, and 9B, the contact ring assemblies 402are retained within the contact retainer 406 by an interference fitbetween the retention tabs 506 of the backing ring 502 and retentionslots 408 in the contact retainer 406. To this end, the distance betweenretention tabs 506 on the same side of the contact ring assembly 402 isslightly less than the width of the distance between retention slots 408in the contact retainer 406, resulting in an interference fit betweenthe assembled components. The interference fit between the retentiontabs 506 of the backing ring 502 and the retention slots 408 of thecontact retainer 406 has the effect of locking the contact ring assembly402 onto the contact retainer 406, which aids the assembly process andadds stability of the contacts within the contact retainer.

With reference to FIGS. 10A and 10B, the operation of the connectorassembly 100 of FIGS. 1-9B is outlined in the following steps:

One or more leads 106 are inserted into an upper seal 204 of a coverassembly 102.

The cover assembly 102 is aligned with and fastened down onto thefeedthrough assembly 104 using the screw 206. As the lower portions ofthe upper seals 204 seat into a respective rectangular recess 308 in thefeedthrough subassembly 302, the upper seals are captured within therecess and thereby are mated to the feedthrough assembly 104.

During fastening of the screw 206, the lower seal 404 of the electricalcontact interposer assembly 304 is squeezed between the contact retainer406 and the feedthrough substrate 310. The contact ring assemblies 402begin to compress as the lead contacts 1002 are forced downward with therest of the cover assembly 102 into the feedthrough assembly 104.

As shown in FIG. 10B, as the torque limit for the screw 206 is reached,the cover 202 is clamped against the feedthrough ferrule 306. The upperseals 204 and the lower seals 404 reach sufficient pressure toelectrically isolate each of the conduction paths through the connectorassembly 100. The contact ring assemblies 402 are compressedsufficiently to establish a reliable electrical connection between firstsurfaces 1004 of the contact ring assemblies and the feedthrough pins312 and between second surfaces 1006 of the contact ring assemblies andthe lead contacts 1002. The super-elastic characteristic of the nitinolbacking ring 502 is able to deform within the radial compressionimparted with the cover 202 fully clamped onto the feedthrough ferrule306. The platinum-iridium contact ring 504 complies with the deflectionof the nitinol backing ring 502 while providing a low resistanceelectrical contact between the lead contact 1002 and the head 314 of thefeedthrough pin 312.

With reference to FIG. 5 , the nitinol backing ring 502 of the contactring assembly 402 exhibits properties of super elasticity which enablethe ring to deform under radial compression without yielding (breaking).An illustration of a theoretical stress—strain curve of super-elasticnitinol is provided in FIG. 11 .

A ring under radial compression is at various stages of stress throughthe stress-strain curve illustrated in FIG. 11 . FIG. 12 illustratesvarious levels of stress of a ring 1202 (half model) under radialcompression as estimated by finite element analysis (FEA). The peakstress is illustrated at the bottom center 1204 of the ring whichcontacts the surface 1206 the ring is pressed against. With reference toFIG. 11 , the nitinol backing ring 502 is configured to stay out of thestage IV region of the stress strain curve (plastic deformation). Theyield strength of Nitinol is approximately 814 MPa, therefore the ring1202 illustrated in FIG. 12 is within the elastic range of the material.The diameter, wall thickness and length of the backing ring 502 can varyto achieve target spring force and elastic range. An illustration of theforce-displacement behavior of different geometries during radialcompression as estimated by FEA is illustrated in FIG. 13 .

With reference to FIGS. 14A and 14B, in some embodiments the contactring assemblies 1400 of an electrical contact interposer assemblyincludes a backing ring 1402 having a split 1408 along the width w andat the bottom center of the ring between the locking tabs 1406, and acontiguous contact ring 1404 similar to the contact ring in FIG. 5 .

The split backing ring 1402 provides some of advantages to the contactdesign. The peek stress on the part illustrated in FIG. 12 is reduced byallowing relative movement across the bottom center of the split backingring 1402. The added compliance of the split backing ring 1402 has thepotential effect of expanding the elastic range of the ring.Additionally, assembly of the split backing ring 1402 and the contactring 1404 is made easier with the split backing ring. The split backingring 1402 can be compressed to accommodate the fit of the contact ring1404 more easily over the backing ring. The split backing ring 1402 andthe contiguous contact ring 1404 would not need to be made with precisediameter dimensions as describe for the contact ring assembly 402 ofFIG. 5 , therefore making fabrication of the contacts easier and lessexpensive. With reference to FIG. 14C, in some embodiments, a splitbacking ring 1410 includes a cutout 1412 formed at one end of the splitring, and a corresponding extension 1414 at the opposite end of the ringthat is sized to fit into the cutout during relative movement of therespective ends.

With reference to FIGS. 15A and 15B, in some embodiments the contactrings assemblies of an electrical contact interposer assembly include abacking ring 1502 a, 1502 b that varies in width around thecircumference of the ring. This contouring around the backing ring 1502a, 1502 b reduces the width w of the ring in the areas where stressesare lowest, therefore providing more deflection in the narrow areas andmore uniform stress throughout the ring under compression. The backingring 1502 b of FIG. 15B includes one or more windows 1504. While notshown in FIGS. 15A and 15B, a contact having a contoured backing ring1502 a, 1502 b also includes a contiguous contact ring similar to thecontact ring 1404 in FIG. 14B and the contoured backing ring 1502 a,1502 b fits within the contact ring.

With reference to FIG. 16 , in some embodiments the contact ringassemblies of an electrical contact interposer assembly include abacking ring 1602 that varies in width around the circumference of thering and includes a split 1608. This contouring around the backing ring1602 reduces the width w of the ring in the areas where stresses arelowest, therefore providing more deflection in the narrow areas and moreuniform stress throughout the ring under compression. While not shown inFIG. 16 , a contact having a split contoured backing ring 1602 alsoincludes a contiguous contact ring similar to the contact ring 1404 inFIG. 14B and the split contoured backing ring fits within the contactring. The split contoured ring of FIG. 16 combine the advantages of boththe split backing ring 1402, 1410 and contoured backing ring 1502 a,1502 b described above into a single backing ring design.

With reference to FIGS. 17A and 17B, in some embodiments the contactring assemblies of an electrical contact interposer assembly include abacking ring 1702 a, 1702 b wherein a significant portion of the ring isremoved to transition from hoop stress to torsional tresses in the ring.These stent backing rings 1702 a, 1702 b result in a substantially lessstiffness in the ring and an extended elastic range of the ring underradial compression. The stent backing ring 1702 a is symmetric withopposed notches 1704 a, 1704 b equally spaced around the circumferenceof the ring that form interconnected rectangular portions 1706, eachwith a window 1708. The stent backing ring 1702 b is asymmetric withnon-aligned notches 1710 a, 1710 b spaced around the circumference ofthe ring. While not shown in FIGS. 17A and 17B, a contact ring assemblyhaving a stent backing ring 1702 a, 1702 b also includes a contiguouscontact ring similar to he contact ring 1404 in FIG. 14B and the stentbacking ring fits within the contact ring and is retained therein by aninterference fit.

With reference to FIGS. 18A, 18B, 19A, and 19B in some embodiments anelectrical contact interposer assembly 1802 includes a lower seal 1804that is placed on the underside of a contact retainer 1806, as opposedto mating with a recess (as in the embodiment of FIG. 4 ). In thisembodiment, the contact retainer 1806 includes ferrule locks 1808 thatalign with notches 1810 around the perimeter of the lower seal 1804. Theferrule locks 1808 secure the lower seal 1804 to the contact retainer1806 through a mechanical, e.g., snap-fit, coupling. With additionalreference to FIG. 3 , the lower seal 1804 provides increased seal widthand thus increased electrical isolation between the heads 314 offeedthrough pins 312 and the contact ring assemblies 402 when a coverassembly is clamped. The lower seal 1804 also minimizes acute pinchingbetween the contact retainer 1806 and the feedthrough substrate 310 of afeedthrough assembly.

The feedthrough assembly 104 of FIG. 3 includes a feedthroughsubassembly 302 having a feedthrough substrate 310 having feedthroughpins 312 with projecting heads 314 that are positioned to contact thecontact ring assemblies 402. With reference to FIG. 20 , in otherconfigurations, the feedthrough assembly 2004 may include a co-fired orleadless feedthrough subassembly 2002. In the leadless feedthroughsubassembly 2002, conductive vias 2006 extend through a feedthroughsubstrate 2008 to form conductive paths having an exposed conductivesurfaces 2014 flush with each side of the feedthrough substrate. In thisfeedthrough assembly 2004, contact ring assemblies 2010 retained in acontact retainer 2012 are positioned adjacent a conductive surface 2014.

B. Feedthrough Assembly with Attached Contacts

In some embodiment the contacts of a connector assembly may bepermanently attached to a feedthrough assembly. For example, thecontacts may be covalently bonded to the feedthrough contacts of thefeedthrough assembly by a laser welding process. Disclosed herein aredifferent configurations of attached contacts. These attached contactsmay be referred to as leaf spring contacts, leaf spring contactassemblies, torsion spring contacts, and torsion spring contactassemblies.

1. Leaf Spring Contact Assemblies

With reference to FIGS. 21-27 , in some embodiments a connector assembly2100 of an implantable medical device includes a cover assembly 2102 anda feedthrough assembly 2104 configured to couple with the coverassembly. The cover assembly 2102 is configured to receive a connectorend of a lead 2110 having lead contacts 2112, and to align the leadcontacts with apertures 2114 of the cover assembly 2102. The feedthroughassembly 2104 includes feedthrough contacts 2108. Attached electricalcontact assemblies 2106 are located on the feedthrough contacts 2108 andin the apertures 2114 when the cover assembly 2102 and feedthroughassembly 2104 are coupled. Each of the attached electrical contactassemblies 2106 includes an attachment feature 2510 permanently coupledto a feedthrough contact 2108 and a contact engagement feature 2512positioned in the aperture 2114.

In the embodiment of FIGS. 21-27 the attached electrical contactassemblies 2106 are configured as leaf spring contact assemblies, andare referred to as compressive contact assemblies in that they areconfigured to be compressed during coupling of the cover assembly 2102and the feedthrough assembly 2104. The leaf spring contact assemblies2106 are attached to feedthrough contacts in the form of conductive viapads 2108 that extend through a feedthrough substrate 2116 of thefeedthrough assembly.

As shown in FIGS. 25-27 , each leaf spring contact assembly 2106includes a compressive contact 2502 and an elastic mount 2504. Theelastic mount 2504 includes the attachment feature 2510, while thecompressive contact 2502 includes the contact engagement feature 2512. Acoupling portion 2506 of the compressive contact 2502 is joined to acoupling portion 2508 of the elastic mount 2504. The coupling portions2506, 2508 may be joined by welding. The elastic mounts 2504 areelectrically coupled through the attachment feature 2510 to conductivevia pads 2108 of the feedthrough assembly by, for example, welding. Thecompressive contact 2502 may be made of 80-20 platinum-iridium alloy.The elastic mount 2504 may be made of 80-20 or 90-10 platinum-iridiumalloy.

Different configurations of feedthrough assemblies having differentconfigurations of leaf spring contact assemblies may be used in place ofthe feedthrough assembly 2104 shown in FIG. 21 . For example, withreference to FIGS. 28-34 , in some embodiments a feedthrough assembly2804 includes leaf spring contact assemblies 2806 that includes acompressive contact 2808 coupled to a U-shaped mount 2810. The U-shapedmount 2810 includes an attachment feature 2816 that attaches tofeedthrough contacts 2812 in the form of conductive via pads 2812extending through a feedthrough substrate 2818 of the feedthroughassembly 2804. The compressive contact 2808 includes a contactengagement feature 2814. With reference to FIG. 32 , coupling features3202 corresponding to edges of the compressive contact 2808 are attachedto coupling features 3204 corresponding to top edges of the U-shapedmounts 2810 by, for example, laser welding to provide electricalcoupling between the U-shaped mount 2810 and the compressive contact2808. The U-shaped mounts 2810 are electrically coupled through theattachment feature 2816 to conductive via pads 2812 of the feedthroughassembly by, for example, welding. The compressive contact 2808 may bemade of 80-20 platinum-iridium alloy. The U-shaped mount 2810 may bemade of 80-20 or 90-10 platinum-iridium alloy.

With reference to FIGS. 35-38 , in some embodiment a feedthroughassembly 3504 includes leaf spring contact assemblies 3506 that includesa compressive contact 3508 and a U-shaped mount 3510. The U-shaped mount3510 includes an attachment feature 3606 that attaches to feedthroughcontacts in the form of conductive via pads 3512 extending through afeedthrough substrate 3518 of the feedthrough assembly 3504. Thecompressive contact 3508 includes a pair of contact engagement features3608, 3610. Similar to the configuration of FIGS. 28-34 , couplingfeatures 3602 corresponding to edges of the compressive contact 3508 areattached to coupling features 3604 corresponding to top edges of theU-shaped mounts 3510 by, for example, laser welding to provideelectrical coupling between the U-shaped mount 3510 and the compressivecontact 3508. The U-shaped mounts 3510 are electrically coupled throughthe attachment feature 3606 to a pair of conductive via pads 3512 of thefeedthrough assembly by, for example, welding. The compressive contact3508 may be made of 80-20 platinum-iridium alloy. The U-shaped mount3510 may be made of 80-20 or 90-10 platinum-iridium alloy.

With reference to FIGS. 37 and 38 , a compressive contact 3508 with thespiral-formed leaves is formed from a flat contact 3702 by bending eachof a narrow end 3704 and a wide end 3706, such that the narrow end restsinside of a window 3708 formed in the wide end.

2. Torsion Spring Contacts and Torsion Spring Contact Assemblies

In the conventional leaf spring contacts, the active length of thespring operates in a bending mode. Achieving adequate active springlength in such contacts becomes challenging when a small leaf contactfootprint is required. The stamped leaf spring contacts disclosed aboveenable adequate contact force and deflection capability in a smallcontact footprint, such as 1 mm×2 mm. However, in order to maximize theactive length of the spring, these leaf spring contacts have significantheight and/or require two piece construction. The contact height and thelimited welding access increase the difficulty of attaching miniatureleaf contacts to the conductive vias in the feedthrough assembly. Freestanding welded miniature contacts are also naturally susceptible todamage due to inadvertent contact, such as may occur during connectionof the leads to the device in a surgical environment.

There is a need for one piece, low profile miniature contacts, withimproved attachability to the conductive vias of the feedthrough andenhanced handling integrity. The torsion spring contacts and torsionspring contact assemblies disclosed below address these needs. Theconnector assemblies disclosed below utilizes torsion spring contactsand torsion spring contact assemblies that are attached directly toconductive vias in the feedthrough or feedthrough pins. The activelength of the torsion spring contacts form an open spring loop or springcoil that is substantially parallel to the surface of the dielectricsubstrate of the feedthrough assembly. This results in a low profile andsmall footprint contact with a substantial active length of the spring.

The torsion spring contacts and torsion spring contact assembliesdisclosed herein have a spring loop or spring coil that has attached endand a free end. On the attached end, there is an attachment feature ortab for attachment to the conductive vias or feedthrough pins. Extendingfrom the free end of the spring coil, is a contact tab or contactengagement feature for making separable pressure connection to therespective proximal contact of the lead. The active spring loop occupiesthe perimeter of the footprint of the torsion spring contact. Theattachment feature and the contact engagement feature are centrallydisposed within the outline of the loop. This maximizes the activelength of the torsion spring contact and provides an ample attachmentaccess, such as may be required by laser welding.

When the torsion spring contact is attached to the conductive vias orfeedthrough pins and a compressive contact force is applied to the tipof the contact engagement feature, the active spring loop behavessubstantially as a single coil of a coil spring. Therefore, the elasticdeflection of the torsion spring contact and the resulting contact forceare primarily due to torsion in the spring loop. In some embodiments,the active spring loop is protectively confined in a counterbore of thedielectric substrate. The walls of the counterbore limit lateralexcursion of the torsion spring contact beyond its elastic limits whenan inadvertent side load is applied to the contact engagement feature.Similarly, a compressive deflection of the torsion spring contact islimited by a predetermined amount of clearance under the contactengagement feature. The twisting of the spring in the active spring loopprovides an elastic deflection and wiping action at the contactinterface. The edge of the contact tip may be coined to a desiredgeometry to increase localized pressure at the interface between thecontact tip and the lead contact.

Various embodiments of torsion spring contacts are disclosed, includingones that attach to brazed feedthrough pins and ones that attach tofeedthrough vias.

With reference to FIGS. 39-50 , in some embodiments a connector assembly3900 of an implantable medical device includes a cover assembly 3902 anda feedthrough assembly 3904 configured to couple with the coverassembly. The cover assembly 3902 is configured to receive a connectorend of a lead 3908 having lead contacts 3910, and to align the leadcontacts with pockets or apertures 4002 of the cover assembly 3902. Thefeedthrough assembly 3904 includes feedthrough contacts 4102 in the formof conductive vias. As shown in FIGS. 41 and 42 , attached electricalcontacts 3912 configured as torsion spring contacts are attached to thefeedthrough contacts 4102 and are located in the apertures 4002 when thecover assembly 3902 and feedthrough assembly 3904 are coupled. Withreference to FIG. 49 , each of the attached electrical contacts 3912includes an attachment feature 4328 permanently coupled to a feedthroughcontact 4102 and a contact engagement feature 4316 positioned in anaperture 4002.

The cover assembly 3902 includes a pair of seals 3906, each configuredto receive a connector end of a lead 3908 that carries a number of leadcontacts 3910. The feedthrough assembly 3904 includes torsion springcontacts 3912 that provide electrical connections between the leadcontacts 3910 and conductive vias 4102 that extend through thefeedthrough assembly. In the configuration of FIG. 39 , there are fourrows of torsion spring contact 3912, with each row having fourassemblies. In FIGS. 41 and 42 , the cover assembly 3902 and thefeedthrough assembly 3904 are coupled, but the cover assembly is notfully secured to the feedthrough assembly. Because the cover assembly3902 and the feedthrough assembly 3904 are not fully secured to eachother, the torsion spring contacts 3912 are not compressed between thelead contacts 3910 and the conductive vias 4102. This uncompressed stateof the torsion spring contacts 3912 may be referred to as a free state.

With reference to FIGS. 43 and 44 , the feedthrough assembly 3904includes a feedthrough subassembly 4302 to which the torsion springcontacts 3912 are permanently attached. The feedthrough subassembly 4302includes a feedthrough ferrule 4306 with a pair of rectangular recesses4308, each with a dielectric, e.g., ceramic, substrate 4310 placedtherein. The dielectric substrate 4310 includes a number of counterbores4312 corresponding in number to the number of torsion spring contacts3912. The base of each counterbore 4312 includes a pair of conductivevias 4102 that pass through the bottom of the dielectric substrate 4310providing electrical conduction paths between opposite sides of thefeedthrough ferrule 4306. The attachment base 4328 of the torsion springcontacts 3912 is permanently attached, e.g., welded, to each conductivevia 4102 within a counterbore 4312 at attachment points 4402.

With reference to FIGS. 43-50 , the torsion spring contacts 3912comprise a continuous piece of material that is bent, shaped, and formedto include a spring loop 4318 having a free side 4326 and an attachedside 4322, and a contact tab or contact engagement feature 4316 thatextends from the free side. An attachment feature 4328, referred to asan attachment base, is included in the attached side 4322. The springloop 4318 has a perimeter with a shape corresponding to the perimetershape of the counterbores 4312 and is sized to fit within thecounterbore. In the configuration of FIGS. 43 and 44 , the perimetershape of the counterbore 4312 and the spring loop 4318 is adiscorectangle, i.e., a geometric shape consisting of a rectangle withtop and bottom lengths whose ends are capped off with semicircles ofradius. Other shapes, however, are possible.

The spring loop 4318 is open (does not form a continuous or closedgeometric shape) and includes spiral portion that extends from theattachment base 4328. The spiral portion spirals from a first linearside 4320 that extends from the attachment base 4328 through a firstsemicircular radius of the attached side 4322, through a second linearside 4324 through a second semicircular radius of the free side 4326,and terminates at the contact engagement feature 4316. The contactengagement feature 4316 projects upward relative to the spring loop 4318and in a direction of an aperture of the cover assembly 6602. Thisformation of the torsion spring contacts 3912 places the edge of thecontact engagement feature 4316 at a location above the top surface ofthe dielectric substrate 4310. The torsion spring contacts 3912 areelectrically coupled to the conductive vias 4102 through the attachmentbase 4328. For example, each end of the attachment base 4328 may belaser welded to a respective one of the conductive vias 4102 at the baseof a counterbore 4312.

With reference to FIG. 45-48 , which show a torsion spring contact 3912in a free state, the torsion spring contact is sized to provideclearance between the perimeter 4502 of the spring loop 4318 and theinner wall 4504 of the counterbore 4312. In the configuration of FIGS.47 and 48 , the torsion spring contact 3912 is formed to have increasedclearance between the free side 4326 of the contact and the inner wall4504 of the counterbore 4312, relative to the clearance of theconfiguration of FIGS. 45 and 46 . The increased clearance allows thefree side 4326 of the torsion spring contact 3912 to be deflectedwithout being obstructed by the walls of the counterbore 4312. Theattached side 4322 of the torsion spring contact 3912 do not movesignificantly and therefore can make a closer fit with the counterbore4312 to better locate the contact.

With reference to FIGS. 51 and 52 , when contact force is applied to thetorsion spring contact 3912, for example, while a cover assembly isbeing secured to a feedthrough assembly, opposed contact forces areapplied to the contact engagement feature 4316 and the attachment base4328. FIG. 51 is an isometric view of the torsion spring contact 3912with contact force applied, showing deflection of the contact andresulting Von Mises stress. FIG. 52 is a side view of the torsion springcontact 3912 with contact force applied, showing deflection of thecontact and resulting Von Mises stress. Defection of the contactprimarily occurs at the contact engagement feature 4316 and the freeside 4326.

FIG. 53 is an illustration of a contact spring flat pattern 5300, or theblank, wherein the horizontal portion 5302 of the blank from which thespring loop 4318 is formed has a variable cross-sectional width, withwider sections corresponding to higher twisting moment (torque), whichoptimizes torsion spring contact parameters. FIGS. 54-58 providevisualization of the torsion spring contact forming steps, showing thatthe two sides of the contact can be formed simultaneously withoutinterference.

With reference to FIGS. 59-62 , in some configurations a connectorassembly includes a cover assembly and a feedthrough assembly havingcontacts 5900 configured as torsion spring contact assemblies thatattach to conductive via pads 4102 at the bottom surface of counterbores4312 in a dielectric substrate 4310.

The torsion spring contact assembly 5900 includes a torsion spring 5902and a weld plate 5904. The torsion spring 5902 comprise a continuouspiece of material that is bent, shaped, and formed to include a springloop 5918 having a free side 5926 and an attached side 5922, and acontact tab or contact engagement feature 5916 that extends from thefree side. An attachment feature 5906, referred to as an attachment end,is included in the attached side 5922. The spring loop 5918 has aperimeter with a shape corresponding to the perimeter shape of thecounterbores 4312 and is sized to fit within the counterbore. In theconfiguration of FIGS. 59-62 , the perimeter shape of the counterbore4312 and the spring loop 5918 is a discorectangle, i.e., a geometricshape consisting of a rectangle with top and bottom lengths whose endsare capped off with semicircles of radius. Other shapes, however, arepossible.

The attachment end 5906 of the torsion spring 5902 is electricallycoupled to the weld plate 5904. To this end, the weld plate 5904 includea slot 5908 into which the attachment end 5906 fits and is secured inplace, for example, by welding. With reference to FIGS. 61 and 62 , theweld plate 5904 is shaped to fit within and locate the torsion springcontact assembly 5900 in a counterbore 4312 of a feedthrough substrateto assure optimum operating clearance for the torsion spring contact.There is a close fit of the weld plate 5904 in the counterbore 4312, anda larger clearance between the free side 5926 of the torsion spring 5902and the side walls of the counterbore.

With reference to FIGS. 63-65 , in some configurations a connectorassembly includes a cover assembly and a feedthrough assembly havingcontacts 6300 configured as torsion spring contact assemblies thatattach to conductive via pads 6502 on a surface a dielectric substrate6504.

The torsion spring contact assembly 6300 includes a torsion spring 6302and a protective shroud 6304. The torsion spring 6302 comprise acontinuous piece of material that is bent, shaped, and formed to includea spring loop 6318 having a free side 6326 and an attached side 6322,and a contact tab or contact engagement feature 6316 that extends fromthe free side. An attachment feature 6306, referred to as an attachmentend, is included in the attached side 6322. The spring loop 6318 has aperimeter with a shape corresponding to the perimeter shape of theprotective shroud 6304 and is sized to fit within the shroud. In theconfiguration of FIGS. 59-62 , the perimeter shape of the protectiveshroud 6304 and the spring loop 6318 is a discorectangle, i.e., ageometric shape consisting of a rectangle with top and bottom lengthswhose ends are capped off with semicircles of radius. Other shapes,however, are possible.

The attachment end 6306 of the torsion spring 6302 is electricallycoupled to the protective shroud 6304. To this end, the protectiveshroud 6304 include a slot 6308 into which the attachment end 6306 fitsand is secured in place, for example, by welding. With reference to FIG.65 , the protective shroud 6304 of the torsion spring contact assembly6300 is welded to conductive via pads 6502 that are co-planar with thetop surface of the dielectric substrate 6504.

With reference to FIGS. 66-71 , in some embodiments a connector assembly6600 of an implantable medical device includes a cover assembly 6602 anda feedthrough assembly 6604 configured to couple with the coverassembly. The cover assembly 6602 is configured to receive a connectorend of a lead 6616 having lead contacts 6618, and to align the leadcontacts with apertures 6614 of the cover assembly 6602. The feedthroughassembly 6604 includes feedthrough contacts 6620 in the form of the tipsof feedthrough pins 6608 that extend into counterbores 6612 of afeedthrough substrate 6610. As shown in FIGS. 66 and 67 , attachedelectrical contacts 6606 configured as torsion spring contacts areattached to the feedthrough contacts 6620 and are located in theapertures 6614 when the cover assembly 6602 and feedthrough assembly6604 are coupled. With reference to FIG. 69 , each of the attachedelectrical contacts 6606 includes an attachment feature 6806 permanentlycoupled to a feedthrough contact 6620 and a contact engagement feature6802 positioned in an aperture 6614.

With reference to FIGS. 68-71 , these torsion spring contact assemblies6606 comprise a continuous piece of material that is bent, shaped, andformed to include a spring loop 6804 having a free side 6814 and anattached side 6810, and a contact engagement feature 6802 that extendsfrom the free side. An attachment tab 6806 is included in the attachedside 6810. The spring loop 6804 has a perimeter with a shapecorresponding to the perimeter shape of the counterbores 6612 and issized to fit within a counterbore. The perimeter shape of thecounterbore 6612 and the spring loop 6804 is a discorectangle, i.e., ageometric shape consisting of a rectangle with top and bottom lengthswhose ends are capped off with semicircles of radius. Other shapes,however, are possible.

The spring loop 6804 is open (does not form a continuous or closedgeometric shape) and includes a spiral portion that extends from theattachment tab 6806. The spiral portion spirals from a firstsemicircular radius of the attached side 6810, through a linear side6812, through a second semicircular radius of the free side 6814, andterminates at the contact engagement feature 6802. The contactengagement feature 6802 projects upward relative to the spring loop 6804and in a direction of an aperture 6614 of the cover assembly 6602. Thisformation of a torsion spring contact 6606 places the edge of thecontact engagement feature 6802 at a location above the top surface ofthe feedthrough substrate 6610. The attachment tab 6806 includes athrough hole 6816 sized to receive the tip of a feedthrough pin 6608.The torsion spring contacts 6606 are electrically coupled to thefeedthrough contacts 6620 through the attachment tab 6806.

The feedthrough pins 6608 aid in positioning of the torsion springcontacts 6606 within the counterbores 6612 and can help to bias theposition of the torsion spring contacts in a manner that increases theclearance between the free side 6814 of the contacts and the inner wallof the counterbores 6612 of the feedthrough substrate 6610.

With reference to FIGS. 72-75 , in some configurations a connectorassembly includes a cover assembly and a feedthrough assembly havingcontacts 7200 configured as torsion spring contacts that attach tofeedthrough pins 7402 with tips 7404 that terminate at or near thebottom surface 7406 of counterbores 7408 in a feedthrough substrate7410.

These torsion spring contacts 7200 comprise a continuous piece ofmaterial that is bent, shaped, and formed to include a spring loop 7204having a free side 7208 and an attached side 7210, and a contact tab orcontact engagement feature 7202 that extends from the free side. Anattachment tab 7206 is included in the attached side 7210. The springloop 7204 has a perimeter with a shape corresponding to the perimetershape of the counterbores 7408 and is sized to fit within a counterbore7408. The perimeter shape of the counterbore 7408 and the spring loop7204 is a discorectangle, i.e., a geometric shape consisting of arectangle with top and bottom lengths whose ends are capped off withsemicircles of radius. Other shapes, however, are possible.

The spring loop 7204 is open (does not form a continuous or closedgeometric shape) and includes a spiral portion that extends from theattachment tab 7206. The spiral portion spirals from a firstsemicircular radius of the attached side 7210, through a linear side7212, through a second semicircular radius of the free side 7208, andterminates at the contact engagement feature 7202. The contactengagement feature 7202 projects upward relative to the spring loop 7204and in a direction of an aperture of the cover assembly. This formationof a torsion spring contact 7200 places the contact engagement feature7202 at a location above the top surface 7412 of the feedthroughsubstrate 7410. The attachment tab 7206 includes a through hole 7216sized to receive the tip 7404 of a feedthrough pin 7402. The torsionspring contacts 7200 are electrically coupled to the tips 7404 of thefeedthrough pins 7402 through the attachment tab 7206.

The feedthrough pins 7402 aid in positioning of the torsion springcontacts 7200 within the counterbores 7408 and can help to bias theposition of the torsion spring contact assemblies in a manner thatincreases the clearance between the free side 7208 of the contacts andthe inner wall of the counterbores 7408 of the feedthrough substrate7410.

With reference to FIGS. 76-79 , in some configurations a connectorassembly includes a cover assembly and a feedthrough assembly havingcontacts 7600 configured as torsion spring contacts that attach tofeedthrough pins 7802 with tips 7804 that terminate at or near themiddle of counterbores 7808 in a substrate 7810.

These torsion spring contacts 7600 comprise a continuous piece ofmaterial that is bent, shaped, and formed to include a spring loop 7604having a free side 7608 and an attached side 7610, and a contact tab orcontact engagement feature 7602 that extends from the free side. Anattachment feature in the form of a curled sleeve 7606 is included inthe attached side 7610. The spring loop 7604 has a perimeter with ashape corresponding to the perimeter shape of the counterbores 7808 andis sized to fit within a counterbore. The perimeter shape of thecounterbore 7808 and the spring loop 7604 is a discorectangle, i.e., ageometric shape consisting of a rectangle with top and bottom lengthswhose ends are capped off with semicircles of radius. Other shapes,however, are possible.

The spring loop 7604 is open (does not form a continuous or closedgeometric shape) and includes a spiral portion that extends from thecurled sleeve 7606. The spiral portion spirals from a first semicircularradius of the attached side 7610, through a linear side 7612, through asecond semicircular radius of the free side 7608, and terminates at thecontact engagement feature 7602. The contact engagement feature 7602projects upward relative to the spring loop 7604 and in a direction ofan aperture of the cover assembly. This formation of a torsion springcontact 7600 places the contact engagement feature 7602 at a locationabove the top surface 7702 of the feedthrough substrate 7810. The curledsleeve 7606 is sized to receive the tip 7804 of a feedthrough pin 7802.The torsion spring contacts 7600 are electrically coupled to the tips7804 of the feedthrough pins 7802 through the curled sleeve 7606.

The feedthrough pins 7802 aid in positioning of the torsion springcontacts 7600 within the counterbores 7808 and can help to bias theposition of the torsion spring contacts in a manner that increases theclearance between the free side 7608 of the contacts and the inner wallof the counterbores 7808 of the feedthrough substrate 7810.

With reference to FIGS. 80-83 , in some configurations a connectorassembly includes a cover assembly and a feedthrough assembly havingcontacts 8000 configured as torsion spring contacts that attach tofeedthrough pins 8102 with tips 8104 that terminate above a top surface8112 a feedthrough substrate 8110.

These torsion spring contacts 8000 comprise a continuous piece ofmaterial that is bent, shaped, and formed to include a spring loop 8004having a free side 8008 and an attached side 8010, and a contact tab orcontact engagement feature 8002 that extends from the free side. Anattachment feature in the form of a curled sleeve 8006 is included inthe attached side 8010. The spring loop 8004 has a perimeter with ashape corresponding to the perimeter shape of the counterbores 8108 andis sized to fit within a counterbore. The perimeter shape of thecounterbore 8108 and the spring loop 8004 is a discorectangle, i.e., ageometric shape consisting of a rectangle with top and bottom lengthswhose ends are capped off with semicircles of radius. Other shapes,however, are possible.

The spring loop 8004 is open (does not form a continuous or closedgeometric shape) and includes a spiral portion beneath the curled sleeve8006. The spiral portion spirals from a first semicircular radius of theattached side 8010, through a linear side 8012, through a secondsemicircular radius of the free side 8008, and terminates at the contactengagement feature 8002. The contact engagement feature 8002 projectsupward relative to the spring loop 8004 and in a direction of anaperture of the cover assembly. This formation of a torsion springcontact 8000 places the contact engagement feature 8002 at a locationabove the top surface 8112 of the feedthrough substrate 8110. The curledsleeve 8006 is sized to receive the tip 8104 of a feedthrough pin 8102.The torsion spring contacts 8000 are electrically coupled to thefeedthrough pins 8102 through the curled sleeve 8006.

The feedthrough pins 8102 aid in positioning of the torsion springcontacts 8000 within the counterbores 8108 and can help to bias theposition of the torsion spring contacts in a manner that increases theclearance between the free side 8008 of the contacts and the inner wallof the counterbores 8108 of the feedthrough substrate 8110.

II. Contacts Associated with Cover Assembly

In some embodiment, detached contacts may be included in the coverassembly component of a connector assembly instead of the feedthroughassembly as disclosed above. These detached contacts are “interposed”between an implantable lead and the implantable device's feedthroughassembly, and form pressure connections between lead contacts andrespective feedthrough substrates. The detached contacts areprotectively retained in the apertures of the seal, which seal ispre-attached to the cover of the cover assembly.

With reference to FIGS. 84-91 , a connector assembly 8400 of animplantable medical device includes a cover assembly 8402 and afeedthrough assembly 8404 configured to couple with the cover assembly.The cover assembly 8402 is configured to receive a connector end of alead 8408 having lead contacts 8410, and to align the lead contacts withpockets or apertures 8414 of the cover assembly. The feedthroughassembly 8404 may include feedthrough contacts 8416 in the form ofconductive vias on the surface of the feedthrough substrate 8420.Electrical contacts 8412 configured as leaf spring contacts are retainedby, but not permanently attached to, the cover assembly 8402. Withreference to FIGS. 87-91 , when the cover assembly 8402 and feedthroughassembly 8404 are coupled, first surfaces 8602, 8604 of the electricalcontacts 8412 face the feedthrough contacts 8416 and at least one secondsurface 8606 of the contacts is positioned in the pockets or apertures8414 of the cover assembly. Upon complete seating of the cover assembly8402 and feedthrough assembly 8404, the first surfaces 8602, 8604 andsecond surface 8606 of the electrical contacts are respectivelycompressed into contact with the feedthrough contacts 8416 and the leadcontacts 8410.

With reference to FIGS. 84 and 85 , the cover assembly 8402 includes apair of seals 8406, each configured to receive a connector end of a lead8408 that carries a number of lead contacts 8410. The seals 8406 includean array of pockets or apertures 8414 each configured to retain a leafspring contact 8412 configured as a leaf spring contact. The leaf springcontacts 8412 provide electrical connections between the lead contacts8410 and conductive vias 8416 that extend through the feedthroughassembly. In the configuration of FIG. 85 , there are four rows of leafspring contacts 8412, with each row having four contacts.

With reference to FIGS. 86A and 86B, in some embodiments the leaf springcontacts 8412 comprise a continuous piece of flat material bent, shaped,and formed to include overlapping tines, each corresponding to a firstsurface 8602, 8604, and a rounded tip corresponding to a second surface8606. The first surfaces 8602, 8604 are configured to couple with a pairof conductive vias 8416 of the feedthrough assembly 8404. The roundedsecond surface 8606 is configured to couple with a lead contact 8410.

In FIGS. 87-89 , because the cover assembly 8402 and the feedthroughassembly 3904 are not fully secured to each other, the leaf springcontacts 8412 are not fully compressed between the lead contacts 8410and the conductive vias 8416. Furthermore, there is a clearance 8802between sides 8804, 8806 of the leaf spring contacts 8412 and the sidewalls 8808, 8810 of the aperture 8414. This clearance 8802 accommodateexpansion of the leaf spring contacts 8412 when the connector assemblyis pressurized (i.e., when the cover assembly is fully seated with thefeedthrough assembly). This uncompressed state (or undeflected state) ofthe leaf spring contacts 8412 may be referred to as a free state or anunpressurized state. In this state, the leaf spring contacts 8412 arenot tightly secured between the lead contacts 8410 and the conductivevias 8416 and may slide and move around within the apertures 8414.

In FIGS. 90 and 91 , because the cover assembly 8402 and the feedthroughassembly 3904 are fully secured to each other by tightening of a screw(not shown) of the cover assembly, the leaf spring contacts 8412 arefully compressed between the lead contacts 8410 and the conductive vias8416. This compressed state (or deflected state) of the leaf springcontacts 8412 may be referred to as a pressurized state. In this state,contact forces exerted on the leaf spring contacts 8412 cause thecontacts to compress vertically between lead contacts 8410 and theconductive vias 8416, as indicated by the vertical arrows, and todeflect or expand horizontally, as indicated by the horizontal arrows.Once fully compressed and deflected, the leaf spring contacts 8412 aretightly secured between the lead contacts 8410 and the conductive vias8416. The clearance 8802 between the sides 8804, 8806 of the leaf springcontact 8412 and the side walls 8808, 8810 of the aperture 8414 remainafter compression because the semi-circular sides of the contact do notexpand when the contact is deflected.

With reference to FIGS. 92 and 93 , the seals 8406 of the cover assembly8402 includes a pair of ledges 9202, 9204 having a taperedcross-section. With reference to FIGS. 94 and 95 , the seals 8406 of thecover assembly 8402 also includes a pair of concave recesses 9402, 9404having a contour generally corresponding to the curvature of the sides8804, 8806 of the leaf spring contact 8412. The ledges 9202, 9204 andthe concave recesses 9402, 9404 function to retain the leaf springcontact 8412 within the aperture 8414. To this end, the seals 8406 areformed of a material, e.g., elastomeric material such as silicone, thatenables the leaf spring contact 8412 to be snapped in place from thefeedthrough side 9208 of the seal, and retained by the ledges 9202, 9204and the concave recesses 9402, 9404.

With reference to FIGS. 96-99 , the leaf spring contact 8412 may haveanyone of several different configurations. In FIG. 96 , the leaf springcontact 9600 has first surfaces 9602, 9604 corresponding to formedcontact tips on the side of the contact that faces the feedthroughassembly, and second surfaces 9606, 9608 corresponding to shearedcontact tips on the side of the contact that faces the lead contacts. InFIG. 97 , the leaf spring contact 9700 is a lower profile contact thathas first surfaces 9702 a, 9702 b, 9704 corresponding to end tines onthe side of the contact that faces the feedthrough assembly, and secondsurfaces 9706, 9708 corresponding to sheared contact tips on the side ofthe contact that faces the lead contacts. The first surfaces 9702 a,9702 b, 9704 are three overlapping end tines that bypass each other anddo not interfere with the opposite side of the contact when the contactis fully compressed.

In FIG. 98 , the leaf spring contact 9800 is a lower profile contactthat has first surfaces 9802, 9804 corresponding to end tines on theside of the contact that faces the feedthrough assembly, and secondsurfaces 9806, 9808 corresponding to sheared contact tips on the side ofthe contact that faces the lead contacts. The first surfaces 9802, 9804are two overlapping end tines that bypass each other and do notinterfere with the opposite side of the contact when the contact isfully compressed. In FIG. 99 , the leaf spring contact 9900 is a lowerprofile contact that has first surfaces 9902, 9904 corresponding tocontact tips on the side of the contact that faces the feedthroughassembly, and a second surface 9906 corresponding to a rounded tip onthe side of the contact that faces the lead contacts. The leaf springcontact 9900 has multiple lengthwise slits 9908, 9910 which increasedeflection compliance of the contact.

III. Comparison to Conventional Connector Assemblies:

A benefit of the connector assemblies disclosed herein is the enablingof a higher density of electrical connections between an implantablemedical device and lead contacts. With reference to FIGS. 100 and 101 ,the connector assemblies disclosed herein allow for more leads to beconnected to a medical device without having to expand the physical sizeof the medical device.

With reference to FIG. 100 , a conventional connector assembly having afeedthrough assembly 10 such as disclosed in U.S. Pat. No. 6,662,035 canaccommodate two leads. The feedthrough assembly 10 includes two lines12, 14 of four stamped compressive leaf contacts 16 attached in place,e.g., welded, to feedthrough contacts (not shown). Each line 12, 14 ofcontacts 16 is arranged to couple with contacts of a single lead. Thecontacts 16 are characterized by a major dimension 18 that is greaterthan a minor dimension 20, and each contact is oriented relative to aline axis 22 for a lead such that its major dimension 18 is transverseto the line axis.

With reference to FIG. 101 , a connector assembly having a feedthroughassembly 30 configured in accordance with embodiments disclosed hereincan accommodate four leads in about the same amount of space as theconventional feedthrough assembly of FIG. 100 . Accordingly, theconnector assemblies disclosed herein can be designed into a modifiedimplantable medical device without having to expand the size of thedevice.

The feedthrough assembly 30 of FIG. 101 includes four lines 32, 34, 36,38 of contacts 40 (instead of only two), where each line of contacts isarranged to couple with the contacts of a lead. In order to double thecontact 40 density, the disclosed feedthrough assemblies use smallercompressive contacts configured as contact rings, contact ringassemblies, leaf spring contacts, torsion spring contacts, or torsionspring contact assemblies, which assure adequate contact deflectioncapability in a smaller contact footprint.

In the feedthrough assembly 30 shown FIG. 101 , the contacts 40correspond to contact rings or contact ring assemblies as describedabove with reference to FIGS. 1-10B and are characterized by a majordimension 42 that is greater than a minor dimension 44, and each contactis oriented relative to a line axis 46 for a lead such that its majordimension 18 is in-line with, or aligned along the line axis. Thisorientation of the contacts 40 enables the inclusion of two dual-lumenseals in a cover assembly (such as shown in FIG. 2B), where each seal isconfigured to receive two leads with lead-to-lead spacing ofapproximately 2 mm. This is in contrast to the transversely orientedcontacts 16 of FIG. 100 which allows only one lead per seal.

In the example feedthrough assembly 30 shown in FIG. 101 , the contacts40 are configured as contact rings (either as a single ring or a ringassembly within a backing ring and a contact ring) and include an axis48 that extends through an opening defined by the structure and shape ofthe ring, e.g., along the center of the ring, and that is transverse theline axis 46 of the lead. This orientation of the contact axis relativeto the line axis is opposite the orientation of the axis 50 of thecontacts 16 of FIG. 100 , wherein the contact axis is aligned with theline axis 22. During compression of the ring contacts 40, such as shownin FIG. 10B, the compressive forces are directed toward the center axis48.

In other configurations disclosed herein, the contacts 40 may beconfigured as leaf spring contact assemblies, such as shown in FIGS.21-36 and FIGS. 84-99 . Like the ring contacts, the leaf spring contactassemblies include a contact axis 48 that extends through an openingdefined by the structure and shape of the leaf spring, and that istransverse the line axis 46 for a lead.

In other configurations disclosed herein, the contacts 40 may beconfigured as torsion-spring contacts such as shown in FIGS. 39-58 andFIGS. 66-83 , or torsion spring contact assemblies such as shown inFIGS. 59-65 . In these configurations, the contacts may be considered toinclude an axis that extends through an opening defined by the structureand shape of the contact, e.g., through the attachment end of thecontact and transverse to the surface of the feedthrough substrate, andthat is also transverse the line axis 46 for a lead. This orientation ofthe contact axis relative to the line axis is different than theorientation of the axis 50 of the contacts 16 of FIG. 100 , wherein thecontact axis is aligned with the line axis 22. During deflection of thetorsion spring contacts, such as shown in FIGS. 51 and 52 , thedeflection forces are directed along the axis of the contact.

The capability of adding leads to a device, e.g., an implantableneurostimulator, enables the device to potentially sense electrographicabnormalities and provide neurostimulation treatment in more locationsof the human body. The additional locations of sensing and treatment hasthe potential to provide broader and better treatment of neurologicaldisorders.

The various aspects of this disclosure are provided to enable one ofordinary skill in the art to practice the present invention. Variousmodifications to exemplary embodiments presented throughout thisdisclosure will be readily apparent to those skilled in the art. Thus,the claims are not intended to be limited to the various aspects of thisdisclosure, but are to be accorded the full scope consistent with thelanguage of the claims. All structural and functional equivalents to thevarious components of the exemplary embodiments described throughoutthis disclosure that are known or later come to be known to those ofordinary skill in the art are expressly incorporated herein by referenceand are intended to be encompassed by the claims. Moreover, nothingdisclosed herein is intended to be dedicated to the public regardless ofwhether such disclosure is explicitly recited in the claims. No claimelement is to be construed under the provisions of 35 U.S.C. § 112,sixth paragraph, unless the element is expressly recited using thephrase “means for” or, in the case of a method claim, the element isrecited using the phrase “step for.”

What is claimed is:
 1. An implantable medical device comprising: atleast one lead including a connector end with a lead contact; a housing;electronics within the housing; a cover assembly having an aperture, thecover assembly configured to receive the connector end of the at leastone lead, and to align the lead contact with the aperture; a feedthroughassembly electrically coupled to the electronics within the housing andconfigured to couple with the cover assembly and including a feedthroughcontact; and a detached electrical contact between the feedthroughcontact and the aperture when the cover assembly and feedthroughassembly are coupled, the detached electrical contact comprising a firstsurface facing the feedthrough contact and a second surface facing theaperture.
 2. The implantable medical device of claim 1, wherein thedetached electrical contact is retained by the feedthrough assembly. 3.The implantable medical device of claim 2, wherein the feedthroughassembly comprises: a feedthrough subassembly having a recess, whereinthe feedthrough contact is within the recess; and a contact interposerassembly configured to retain the detached electrical contact and to beretained in the recess to align the detached electrical contact with thefeedthrough contact.
 4. The implantable medical device of claim 3,wherein the detached electrical contact comprises: a contact ring; and abacking ring configured to fit inside the contact ring and be retainedtherein by a slip fit or an interference fit.
 5. The implantable medicaldevice of claim 4, wherein the backing ring is further configured toprovide an interference fit between itself and the contact interposerassembly.
 6. The implantable medical device of claim 5, wherein theinterference fit is provided by a plurality of space apart tabsassociated with the backing ring, wherein the spaced apart tabs extendinto a cutout of the contact interposer assembly and a space between thespaced apart tabs provides the interference fit with the cutout.
 7. Theimplantable medical device of claim 4, wherein: the contact ring iscontinuous, and the backing ring is one of continuous or discontinuous,and is characterized by one or more of: a varying width around thecircumference, a window through a thickness of the backing ring, and aplurality of notches spaced around the circumference.
 8. The implantablemedical device of claim 1, wherein the detached electrical contact isretained in the aperture of the cover assembly.
 9. The implantablemedical device of claim 8, wherein the cover assembly comprises a sealhaving a lumen for receiving the connector end of the at least one lead,and at least one aperture orthogonal to the lumen and configured toretain the detached electrical contact.
 10. The implantable medicaldevice of claim 1, wherein: the feedthrough contact comprises a pair ofconductive vias; and the detached electrical contact comprises a pair ofoverlapping tines corresponding to the first surface of the detachedelectrical contact and a rounded tip corresponding to the second surfaceof the detached electrical contact, wherein each of the tines isconfigured to couple with a corresponding one of the pair of conductivevias.
 11. The implantable medical device of claim 1, wherein thedetached electrical contact is not bonded or welded to the feedthroughcontact.
 12. The implantable medical device of claim 1, wherein thedetached electrical contact is configured to allow for a compressionconnection with the feedthrough contacts when the cover assembly iscoupled to the feedthrough assembly.
 13. An implantable medical devicecomprising: at least one lead including a connector end with a leadcontact; a housing; electronics within the housing; a cover assemblyhaving an aperture, the cover assembly configured to receive theconnector end of the at least one lead, and to align the lead contactwith the aperture; a feedthrough assembly electrically coupled to theelectronics within the housing and configured to couple with the coverassembly and including a feedthrough contact; and an attached electricalcontact between the feedthrough contact and the aperture when the coverassembly and feedthrough assembly are coupled, the attached electricalcontact comprising an attachment feature permanently coupled to thefeedthrough contact and a contact engagement feature facing theaperture.
 14. The implantable medical device of claim 13, wherein thefeedthrough assembly comprises a counterbore and the feedthrough contactis within the counterbore.
 15. The implantable medical device of claim13, wherein the attached electrical contact comprises: a generallyc-shaped elastic mount comprising the attachment feature and a firstportion; and a compressive contact comprising the contact engagementfeature and a second portion electrically coupled to the first portionof the elastic mount.
 16. The implantable medical device of claim 13,wherein the attached electrical contact comprises: a generally u-shapedmount comprising the attachment feature and a coupling feature; and acompressive contact comprising the contact engagement feature and acoupling feature electrically coupled to the coupling feature of themount.
 17. The implantable medical device of claim 13, wherein theattached electrical contact comprises a continuous piece of materialformed to include: the contact engagement feature; and a spring loophaving a free side, and an attached side comprising the attachmentfeature, wherein the contact engagement feature extends from the freeside in a direction of the aperture.
 18. The implantable medical deviceof claim 17, wherein the feedthrough contact comprises one of afeedthrough via and a feedthrough pin.
 19. The implantable medicaldevice of claim 13, wherein the attached electrical contact comprises: aweld plate comprising the attachment feature; and a continuous piece ofmaterial formed to include: the contact engagement feature; and a springloop having a free side, and an attached side electrically coupled tothe weld plate, wherein the contact engagement feature extends from thefree side in a direction of the aperture.
 20. The implantable medicaldevice of claim 13, wherein the attached electrical contact comprises: ashroud comprising the attachment feature; and a continuous piece ofmaterial formed to include: the contact engagement feature; and a springloop at least partially within the shroud and having a free side, and anattached side electrically coupled to the shroud, wherein the contactengagement feature extends from the free side in a direction of theaperture.